Cooling of electronic components with free jet impingement boiling

Abstract

With the ever increasing heat dissipation rate and heat flux in electronic components, new cooling technologies need to be developed. This paper presents an experimental study of two phase boiling heat transfer in free jet impingement. In the experiments with a thick film resistor, the effect of jet velocity and subcooling was studied. Boiling curves were obtained from the experimental results. A higher velocity led to a higher heat transfer coefficient in single phase heat transfer while jet diameter has very little effect on single phase heat transfer. Boiling with a higher velocity and a larger jet diameter results in a higher heat transfer coefficient although effect of velocity is less significant at boiling. Active nucleation sites distribution from probabilistic effect and surface condition may have strong influence on the boiling heat transfer. Subcooling has apparent effects on boiling heat transfer by changing flow and thermal patterns. Critical heat flux (CHF) was found to increase with increasing jet velocity, jet diameter and jet inlet subcooling. In experiments with a thermal test die which was capable of capturing the temperature pattern on the heated surface, a near uniform temperature pattern was obtained at low heat flux when there was only single phase heat transfer. Non-uniformly distributed temperatures were found on the surface during boiling. Boiling was activated somewhere on the surface first, leading to a lower temperature locally. Boiling and non-boiling regions co-exist on the surface. Nucleation spreads out the whole surface with larger heat flux, leading to the vanishing of well-regulated temperature patterns. The non-uniform temperature distribution at jet impingement boiling may cause additional thermal stress on the chip package.